This invention relates to a vacuum-type circuit interrupter and, more particularly, to a vacuum-type interrupter that includes a plurality of spaced-apart pairs of separable contacts electrically connected in parallel for carrying current through the interrupter when closed.
In most interrupters, the force required to hold a pair of separable contacts in engagement during the passage of high current therethrough varies directly with the square of the current. It has been recognized that this force can be reduced by providing a plurality of sets of contacts electrically connected in parallel for sharing the total current through the interrupter. But this approach involves a number of problems. First of all, if the movable contact of each pair is mounted on the usual long, slender contact rod and these contact rods are arranged side-by-side, magnetic forces developed between the contact rods when high currents flow therethrough tend to force the rods together, making it difficult to properly guide and operate the rods. Another problem with parallel-connected contacts is that it is difficult during interrupting operations to consistently develop arcs at all the pairs of contacts for sharing the total arcing current through the interrupter. If arcs are developed at less than all of the contact pairs, the pair, or pairs, that do arc can be forced to carry unduly high currents through their associated arcs.